Use of the 'low-salt-in strategy' of haloadaptation with accumulation of organic osmotic solutes is widespread in the small subunit rRNA sequence-based phylogenetic tree of life (Fig. (Fig.5).5). Not all groups of halophiles have yet been examined for the occurrence and distribution of organic solutes. For example, no information is available on the composition and concentrations of intracellular solutes within the recently characterized extremely halophilic flagellate protozoa [14,15]. We do, however, have a quite complete picture of the distribution of organic solutes in most other groups of halophilic microorganisms. Glycerol and other polyols are widely used for osmotic adaptation in halophilic eukaryotic algae and fungi, but only seldom in the the prokaryotes, the finding of mannitol in Pseudomonas putida [51] being a notable exception. The occurrence of certain other solutes in halophilic and halotolerant prokaryotes is also often correlated with their position in the phylogenetic tree of life.